For some reason the developers refuse to allow this, and last I checked the form fields were not of the proper type for some apps to remember the username/pass on your behalf. Here is what I have done:

1) Create a new text file anywhere on your computer, like in c:\FILES. Rename it to fitday.html

Be sure to replace PUTYOURUSERNAMEHERE with your username and PUTYOURPASSWORDHERE with your password.

3) Bookmark this in your browser: file:///C:/FILES/Fitday.html. This book mark now calls that local file with your username/pass hard-coded and the javascript automatically submits. I'd say 1/8 times or so this doesn't submit properly due to an error at fitday.com, so just hit the book mark again and you're good.

This file recreates the functionality of the fitday.com login page, and submits your username/pass to the same page the normal login page does. The page AFTER the regular fitday.com login doesn't care who submitted the username/pass, just that they are submitted, so in this case you're submitting it from your local machine. This won't affect any functionality whatsoever once you're logged in to fit day.